The ankle joint is one of the most frequently sprained joints in the body. External rotation of the ankle or turning the foot outwardly is known as eversion or supination, and internal rotation of the ankle or inward turning of the foot is known as inversion or pronation.
Very few injuries to the muscles and tendons of the ankle occur from eversion; rather the majority of ankle sprains are caused by excessive inversion, damaging ligaments of the lateral complex. The three ligaments making up the lateral complex (lateral collateral ligaments) are: posterior talofibular, calcaneofibular and anterior talofibular. The most frequently damaged ligaments are the anterior talofibular (E) and the calcaneofibular (F), shown in FIG. 13. The occurrence of injuries to these two ligaments can be reduced by restricting inversion.
It is very important when restricting inversion that plantar and dorsi flexion are not hindered, as this leads to decreased performance during athletic activity. The axis of motion for foot plantar and dorsi flexion occurs just inferior to the lateral malleolus. This "pivot point" must be taken into consideration when any restrictive devices are applied to the ankle. Any pivot point on a restrictive device must be aligned with the axis of motion of the ankle.
Prior art devices and methods for minimizing the risk of sprained ankles include taping the ankle to immobilize it against excessive internal rotation, and support systems built into shoes. Taping the ankles of athletes is a time consuming and expensive procedure. It generally cannot be accomplished properly by the athlete himself, but rather requires a trainer with special knowledge of how to tape ankles properly in order to effectively protect the ankle.
Athletic shoes have attempted to deal with this problem. Traditional shoe support systems addressing ankle motion control have used either rigid members, elastic materials, or straps to provide ankle support. These systems have not addressed several key factors; i.e., the need for individual adjustment of the amount of inversion support, the desirability of restricting only inversion, and positioning the foot in a properly supinated position when landing to help prevent fallover.
Recent attempts to incorporate ankle support members and braces into shoes either insufficiently prevent inversion or impede plantar flexion, dorsi flexion, and eversion. U.S. Pat. No. 3,327,410 to Park, Sr., et. al., discloses a hightop athletic shoe having two strap members anchored to opposite sides of the sole on the inside of the shoe. These straps impede plantar flexion and tend to cut off circulation to the foot. U.S. Pat. Nos. 4,547,981 to Thais et. al., and 4,577,419 to Chassaing disclose hightop athletic shoes with one strap ankle protectors. Both of these shoes use only one strap wrapped around the outside of the shoe rather than directly around the leg to support the ankle. Because the straps are wrapped around the outside of the shoe rather than directly around the leg, they do not properly conform to the leg and therefore, cannot provide adequate support. Inadequate ankle support also occurs because the shoes use only a single strap, which must be relatively long, and the excess length of the single strap results in excessive play.
U.S. Pat. No. 4,556,054 to Paulseth discloses an ankle orthosis with an ankle cuff, a foot plate and a means of connection between the two. This device incorporates a strap connected to the rearward lateral portion and the forward lateral portion of the foot plate. A strapping mechanism such as this, with two widely spaced originating points on the lateral side, will restrict plantar and dorsi flexion. The pivot point of this device does not align with the axis of motion of the ankle. Also, unlike the ankle with its constant pivot point, this device's pivot point grossly alters position during plantar and dorsi flexion.